In an Institute of Electrical and Electronics Engineers (IEEE) 802.16m system, a frame includes a plurality of subframes, each subframe having a plurality of subcarriers along a frequency axis and a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols along a time axis. Some of the subframes in a frame are used for UpLink (UL) data transmission and the other subframes are used for DownLink (DL) data transmission. The IEEE 802.16m frame structure will be described below in brief.
FIG. 1 illustrates a basic frame structure in the IEEE 802.16m system.
Referring to FIG. 1, each 20-ms superframe is divided into four equal 5-ms frames, each having one of channel bandwidths 5, 10 and 20 MHz. According to its channel bandwidth, a 5-ms frame may include 7 or 8 subframes.
A subframe may be allocated for DL or UL transmission. According to their channel bandwidths, subframes may include different numbers of Orthogonal Frequency Division Multiple Access (OFDMA) symbols. Type-1, type-2 and type-3 subframes may be defined as subframes including 6, 7 and 5 OFDM symbols, respectively.
A Base Station (BS) may transmit system information and control information on control channels, and transmit data in the remaining frame regions except for the control channels to MSs in the frame structure. The control channels include a SuperFrame Header (SFH), an Advanced-MAP (A-MAP), etc.
Among the control channels, the SFH is divided into two parts, a Primary SFH (P-SFH) and a Secondary SFH (S-SFH). The SFH broadcasts mandatory or optional system information. Specifically, the BS may help an MS with initial network entry upon power-on, network reentry, and handover when the MS is moving, by transmitting an SFH to the MS.
As illustrated in FIG. 1, an SFH may be distributed at the starts of superframes. Alternatively, an SFH may be locally allocated in a predetermined region in the frame structure. In the latter case, there exists a need for a technique for allocating resources to the remaining region except for a region carrying an SFH, for efficient data transmission, and signaling the resource allocation by the SFH.
However, no studies have been made so far on techniques for allocating resources to the other subframes except for a subframe carrying an SFH and signaling the resource allocation.
As described above, an SFH (particularly, an S-SFH) or a Broadcast CHannel (BCH) is used to broadcast mandatory or optional system information to MSs. Accordingly, the S-SFH or the BCH needs robust transmission. To ensure the robustness, the S-SFH or the BCH needs to be transmitted repeatedly. Without knowledge of the repetition number of the S-SFH or the BCH, an MS suffers from great inefficiency of decoding received information.
Although the decoding inefficiency degrades the communication performance of the MS, there have not been studies to overcome the performance degradation.